Patch "iommu/vt-d: Improve ITE fault handling if target device isn't present" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    iommu/vt-d: Improve ITE fault handling if target device isn't present

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iommu-vt-d-improve-ite-fault-handling-if-target-devi.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7487a47a96d920756c3a962662cbe8cc489e1d39
Author: Ethan Zhao <haifeng.zhao@xxxxxxxxxxxxxxx>
Date:   Tue Mar 5 20:21:16 2024 +0800

    iommu/vt-d: Improve ITE fault handling if target device isn't present
    
    [ Upstream commit 80a9b50c0b9e297669a8a400eb35468cd87a9aed ]
    
    Because surprise removal could happen anytime, e.g. user could request safe
    removal to EP(endpoint device) via sysfs and brings its link down to do
    surprise removal cocurrently. such aggressive cases would cause ATS
    invalidation request issued to non-existence target device, then deadly
    loop to retry that request after ITE fault triggered in interrupt context.
    this patch aims to optimize the ITE handling by checking the target device
    presence state to avoid retrying the timeout request blindly, thus avoid
    hard lockup or system hang.
    
    Devices TLB should only be invalidated when devices are in the
    iommu->device_rbtree (probed, not released) and present.
    
    Fixes: 6ba6c3a4cacf ("VT-d: add device IOTLB invalidation support")
    Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
    Signed-off-by: Ethan Zhao <haifeng.zhao@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240301080727.3529832-4-haifeng.zhao@xxxxxxxxxxxxxxx
    Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
    Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index f9b63c2875f71..ad8a340fc7f1d 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1272,6 +1272,8 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
 {
 	u32 fault;
 	int head, tail;
+	struct device *dev;
+	u64 iqe_err, ite_sid;
 	struct q_inval *qi = iommu->qi;
 	int shift = qi_shift(iommu);
 
@@ -1316,6 +1318,13 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
 		tail = readl(iommu->reg + DMAR_IQT_REG);
 		tail = ((tail >> shift) - 1 + QI_LENGTH) % QI_LENGTH;
 
+		/*
+		 * SID field is valid only when the ITE field is Set in FSTS_REG
+		 * see Intel VT-d spec r4.1, section 11.4.9.9
+		 */
+		iqe_err = dmar_readq(iommu->reg + DMAR_IQER_REG);
+		ite_sid = DMAR_IQER_REG_ITESID(iqe_err);
+
 		writel(DMA_FSTS_ITE, iommu->reg + DMAR_FSTS_REG);
 		pr_info("Invalidation Time-out Error (ITE) cleared\n");
 
@@ -1325,6 +1334,19 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index)
 			head = (head - 2 + QI_LENGTH) % QI_LENGTH;
 		} while (head != tail);
 
+		/*
+		 * If device was released or isn't present, no need to retry
+		 * the ATS invalidate request anymore.
+		 *
+		 * 0 value of ite_sid means old VT-d device, no ite_sid value.
+		 * see Intel VT-d spec r4.1, section 11.4.9.9
+		 */
+		if (ite_sid) {
+			dev = device_rbtree_find(iommu, ite_sid);
+			if (!dev || !dev_is_pci(dev) ||
+			    !pci_device_is_present(to_pci_dev(dev)))
+				return -ETIMEDOUT;
+		}
 		if (qi->desc_status[wait_index] == QI_ABORT)
 			return -EAGAIN;
 	}